NG (No Gum) is what happens when a stamp has no adhesive. Early stamps were made without gum on them, so the user needed to have his own glue or paste to affix the stamp to the envelope. This might be that it went through the mail without being cancelled and was soaked off the envelope, or it got wet and lost it. OG (Original Gum) is obviously worth more to a collector.
OG means Original Gum. This indicates the stamp has never been used and has been kept away from moisture so that the gum applied when the stamp was made is still intact.
stamp collecting
MNH means Mint - Never Hinged. That means the original gum is intact and has not been damaged by the use of a hinge, a mounting method that can leave residue and remove some of the original gum.
Litho in stamp collecting refers to the printing process called offset lithography.
Kenneth F. Chapman has written: 'Good stamp collecting' -- subject(s): Collectors and collecting, Stamp collecting
Margaret I. Morris has written: 'Thematic stamp collecting' -- subject(s): Stamp collecting
Walter Young has written: 'Stamp collecting, A to Z' -- subject(s): Stamp collecting
Stamp collecting
because stamp were easily obtained .
Edward H. Spire has written: 'Adventures in stamp collecting' -- subject(s): Stamp collecting
It depends on whether they have been used or not. If they have original gum they would be considered mint. The value could depend on the cancellation and how rare it is.
James Watson has written: 'The Stanley Gibbons book of stamps and stamp collecting' -- subject(s): Postage stamps, Stamp collecting 'The Stanley Gibbons book of stampsand stamp collecting' -- subject(s): Collectors and collecting, Postage-stamps 'Your book of stamps' -- subject(s): Stamp collecting 'Modern 8mm cine-photography' -- subject(s): Amateurs' manuals, Cinematography